DC - DC Charger Project

[Yoda]

Well after reading howson Howard's tutorial - https://gdrvowners.com/forum/operati...e-battle-borns and many others I have decided this will be a good project for my new truck and plan on what I need to complete the project, This time getting only what I need. Thanks to everyone for the parts list and links.

First DC-DC charger selection.

How big do I REALLY need? I want to charge batterys and run fridge using my Multiplus. I usually drive 6 to 10 hours a day. So far solar has kept everything up, but I am not trying to run the fridge yet Fridge is Dometic single door DM2862RBFX https://www.dometic.com/en-ca/outdoo...-2882-_-183126

Input voltage (AC) 120 V
Input voltage (DC) 12 V
Rated input current (AC) 2.7 A
Rated input power (AC) 440 W
Input frequency 60 Hz

From rough numbers the 30A charger should handle it. Assuming 120V. at 2.7A is 27A at 12V or 24A at 13.4V I need to run a teas with the multi plus, but couldn't today as I have hard switch set to charger only (did not have cargo key with me) and touch 50 would not turn the inverter on for some reason. Amway once I get it to fire up I was going to see the change in power usage for inverter on with fridge off, then with fridge on. Is my math correct? Remember I have solar on top of this.

BTW - I noticed only one solar panel was providing any input (batterys at 100% ) Both MPPT's are set to the same profile - bigger unit is controlling - both on per Multiplus. I guess I should take some screen shots.

Renogy has 3 units out there 20A, 40A, and 60A - well documented in Howard's write up. Can be set for various battery types, but not fully programmable
https://www.renogy.com/battery-charg...rt=bestselling

Victron Energy has 12/12-18 and a 12/12-30 Bluetooth and Victron connect compatible and charge profile is customizable - about twice the cost of the Renogy.

So first question is what do I need and which unit should I get?

Second is wire sizing. If i go withe Victron 30A unit
it appear I can go with 6AWG wire. F350 CC long bed with 5th wheel should be about 25' -30' battery to battery. Am I correct on this or just plan o 4 awg as others have used? I know I would need 4awg for the 40A or 60A Renogy.

Thanks for getting me off on the correct foot
Keith

[Country Campers]

Yoda

This is good timing as I have been pondering a similar setup for my new battery system. I believe that Guest Jim has installed and is using a Renogy 20 amp for his single battery setup with the stock wiring on his truck with no issues. I will be following closely to see if I will go with your setup or choose another way, it is nice to have a large test base with this Forum.

Brian

[Jlawles2]

Yoda Keith, I would measure from one battery to the 7 way RV trailer plug by using a fiberglass tape and following the same route that you will put the wire. From there use the RV side of the 7 way plug as a reference for the 12 VDC interconnect cable up to where the DC-DC unit will be mounted. Add these 2 numbers together. It may not be the right thought, but if the 7 way has not been too short for any situation you have been in, the 12VDC interconnect cable should be safe also at the same length.

I'd consider one of these for the interconnect cable end:https://www.amazon.com/POLLAK-2-Pole.../dp/B078WD7792 and the mating vehicle side https://www.amazon.com/POLLAK-2-Pole...78WD8X3K&psc=1

[acoleman43]

Yoda How many amps do you have available from the alternator of you tow vehicle?

[Jimmer]

For reference, I went with a Renogy 60amp DC/DC charger. I'm using 2 gauge wire wire and a Mechman 320 amp aftermarket alternator. I'm pulling 86 amps out of the truck to get 60 amps out of the Renogy. Of course, I can switch the charging from 60amps to 30 amps. I'm using the Keyline Iso-Pro 140 battery isolator which is connected to ground through a switch on the dash in my truck. I don't have any solar (yet) so I wanted maximum charging of the 5 Battleborn 100ahour batteries in my RV. I'm very happy with this setup.

[Yoda]

Yoda Keith, I would measure from one battery to the 7 way RV trailer plug by using a fiberglass tape and following the same route that you will put the wire. From there use the RV side of the 7 way plug as a reference for the 12 VDC interconnect cable up to where the DC-DC unit will be mounted. Add these 2 numbers together. It may not be the right thought, but if the 7 way has not been too short for any situation you have been in, the 12VDC interconnect cable should be safe also at the same length.

I'd consider one of these for the interconnect cable end:https://www.amazon.com/POLLAK-2-Pole.../dp/B078WD7792 and the mating vehicle side https://www.amazon.com/POLLAK-2-Pole...78WD8X3K&psc=1

Now that would make the in bed connection a snap - Thanks. I guess I could use 4/2 or 6/2 SOOW cable to the trailer too. Thanks for the wiring length tip - I'm guessing it is now about 30' give or take (so 4/0 range). I'll measure my old truck to see. By the time I run two welding cables plus loom I am near the SOOW cable price too.

Thanks Joseph
Keith

[Yoda]

Yoda How many amps do you have available from the alternator of you tow vehicle?

It should be 397 amp if the order guide is correct. Comes with the in cab instant heat option on the diesel.

[Jlawles2]

Yoda Keith, I was looking for a 2 pole twist lock like we use at work when the class 8 power wires for trailers crossed my mind. Someone probably makes a smaller amperage one that may be cheaper, but those are pretty easy to get at a farm and ranch store or truck stop should something happen.

[acoleman43]

It should be 397 amp if the order guide is correct. Comes with the in cab instant heat option on the diesel.

With the 397 amp alternator, you should be able to choose whatever charger you want

I like Victron so my vote is for the Victron 12/12-30

[Yoda]

Yoda Keith, I was looking for a 2 pole twist lock like we use at work when the class 8 power wires for trailers crossed my mind. Someone probably makes a smaller amperage one that may be cheaper, but those are pretty easy to get at a farm and ranch store or truck stop should something happen.

Found these on ZORO Says US made??? 1/2 Pollak price
https://www.zoro.com/grote-trailer-p...59/?q=82-1042v
https://www.zoro.com/grote-trailer-s...029/?q=82-1041

Horizontal pin similar to Pollak
https://www.zoro.com/grote-socket-2-...41/i/G5965878/
https://www.zoro.com/grote-plug-wspr...887/?q=82-1042

Not sure which is better

[Jlawles2]

Not certain what is the most common. Might want to look at a truck stop or your local parts store and see what they have hanging on the wall.

[wygieman]

For reference, I went with a Renogy 60amp DC/DC charger. I'm using 2 gauge wire wire and a Mechman 320 amp aftermarket alternator. I'm pulling 86 amps out of the truck to get 60 amps out of the Renogy. Of course, I can switch the charging from 60amps to 30 amps. I'm using the Keyline Iso-Pro 140 battery isolator which is connected to ground through a switch on the dash in my truck. I don't have any solar (yet) so I wanted maximum charging of the 5 Battleborn 100ahour batteries in my RV. I'm very happy with this setup.

I have the 60 amp Renogy also only I went with 4 awg wire. It draws approximately the same 85 amps supplying 60 amps to the batteries. Since the Renogy is already controlling the voltage, the voltage drop on the wire isn’t critical, only the ampacity. I believe with my short bed, the total run was 40+ feet. I didn’t have much wire left from a 50 foot spool. Simple to have a switch on the Renogy to select 30 or 60 amp and it is nice to have the option when you need power. Note that the Renogy can also be a power supply in addition to being a battery charger, don’t know about the Victron.

[Yoda]

I have the 60 amp Renogy also only I went with 4 awg wire. It draws approximately the same 85 amps supplying 60 amps to the batteries. Since the Renogy is already controlling the voltage, the voltage drop on the wire isn’t critical, only the ampacity. I believe with my short bed, the total run was 40+ feet. I didn’t have much wire left from a 50 foot spool. Simple to have a switch on the Renogy to select 30 or 60 amp and it is nice to have the option when you need power. Note that the Renogy can also be a power supply in addition to being a battery charger, don’t know about the Victron.

Thanks
I was not aware of the current limitation feature - you made me read the manual

Keith

PS Good thing I can think on this a while

[ncitro]

Yoda Getting caught up on the forum after being on a trip for a few days. Good advice here, I have the Renogy 40A. The 60 had just come out when I bought mine and the book said to only use short wire runs with it (I think it was mainly targeted to motorhomes and vans), but I think that has since been lifted. I run 4AWG wire on mine, and ocassionally tripped the 60 amp breaker I put up by the battery. I have increased this to 100 amps (still well within the 4awg current rating) and have not had a problem since. My longbed took a lot of wire, but I had to cross laterally as well since I located the breakers and connection point by the passenger battery, and put my connection point by the 7 pin bed connector on the driver side. I think I bought 50 foot of each (red/black welding from Windy Nation on Ebay) and used it all on the truck. I then used some wire I had around the shop for the run from the pinbox back to the batteries.

I used the Andersen SB120 connectors and they have been great. I found a guy who 3d prints a panel mount, which I cut out the side of the bed for (a scary hole to cut for sure lol) and it works great.

[Jimmer]

I have the 60 amp Renogy also only I went with 4 awg wire. ...

That's good for everyone to know that the 60 amp Renogy works just fine with 4 gauge wire. The Renogy manual implies that 4 gauge is only good for up to 8 feet with the 60 amp charger, not the 40 feet that we need. Of course, since the DC/DC converter bumps up any voltage drop, so the wire gauge from the truck is clearly not critical. Although I don't know if I'd want to go to a smaller wire than 4 gauge for the 60 amp.